JTMSK: Possible New Mode for Meteor Scatter
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1. Transmitting

Messages are sent character-by character, 6 bits plus odd parity.
Message length can be one of {5 7 9 11 13 17 19 23 29}; messages are
padded with blanks up to the next available length from this list.

Modulation is Minimum Shift Keying (MSK) at 2000 baud.  This is a form
of constant-envelope, continuous-phase modulation, equivalent to FSK
with offset equal to half the bit rate.  JTMSK sends a "0" bit with
0.5 ms of a sine wave at f0=1000 Hz, and a "1" bit at f1=2000 Hz.
Carrier phase increment over one bit is therefore 0.5 cycles (pi
radians) at f0 and 1.0 cycles (two*pi radians) at f1.  With odd parity
there is always an odd number of 1's and even number of 0's in a
character, so the phase increment over a full character is always an
integer number of cycles.

2. Receiving

  a. Pings are detected (or mouse-picked data is selected) as in
     WSJT9, except that it's done in real time rather than at the end
     of an Rx interval.  

  b. Compute real-to-complex FFT.  Zap birdies, remove frequency 
     components outside the range 300 - 2700 Hz, and convert to analytic
     time-domain signal.  (analytic)

  c. Square the complex signal, cx2=cx*cx, and compute FFT.  Look for
     narrow carriers at frequency 2000 + 2*DF +/- 2*Tol and 2000 Hz
     higher.  (msdf)

  d. If carrier is found, measure frequency f and phase phi.  Multiply
     cx by exp(-twopi*i*(f-1500)*t - phi) to recover the
     standard-frequency baseband signal.  (tweak1)

  e. Establish symbol and character sync by cross-correlating with
     conjg(cwb), where cwb is the MSK waveform for the <space>
     character.

  f. Find message length by computing ACF (of what?  cdat?  soft
     symbol values?)
 
  g. Cross-correlate the complex standard-frequency signal against
     conjugated templates for each character in the JTMSK alphabet.
     Best match yields the decoded character.

  h. Decode the message by cross-correlating character-length segments
     of cdat against complex waveforms for each possible character.

  i. If msglen is established and long enough, try folding the data and
     determining best-fit characters as above.

3. Comparison of modes:

                   |    Meteor Scatter     |    IonoScatter
                   |  FSK441  JTMS  JTMSK  |   JT6M    ISCAT
-------------------+-----------------------+-------------------
T/R period (s)     |    30     30    30    |    30       30
Modulation type    |  4-FSK   MSK*  MSK*   |  44-FSK    41-FSK
Keying rate (baud) |   441   1378  2000    |   21.5     43.1
Characters/s       |   147    197   286    |   14.3     32.3
Bandwidth (Hz)     |  1764   1378  2000    |   947      1809